intro to pedigree and mendelian genetics

Question 1

set of alleles that make up a persons genetic constitution

Answer 1

genotype

Question 2

the observable expression of a genotype as a morphological, clinical cellular, or biochemical trait

Answer 2

phenotype

Question 3

when a gene influences multiple, seemingly unrelated phenotypic traits

Answer 3

pleiotropic genes

Question 4

single gene disorders are determined

Answer 4

at a single locus

Question 5

pair of identical alleles

Answer 5

homozygous

Question 6

two different alleles

Answer 6

heterozygous

Question 7

two different mutant alleles are present

Answer 7

compound heterozygote

Question 8

used for dudes, who have only one X chromosome

Answer 8

hemizygous

Question 9

summary of details of a family in graphical form

Answer 9

pedigree

Question 10

the person of interest (brought to the attention) to the geneticist

Answer 10

proband (syn. prospositus, index case)

Question 11

couples with one or more ancestors in common

Answer 11

consanguineous

Question 12

person who brings the family to the attention of the geneticist

Answer 12

consultand (can be affected or unaffected or unrelated)

Question 13

single gene disorders are called

Answer 13

Mendelian disorders

Question 14

dominant phenotype

Answer 14

expression when one mutant and one WT allele

Question 15

expression only when chromosome pair carries two mutant alleles

Answer 15

recessive

Question 16

both traits (alleles) are expressed in the heterozygous state

Answer 16

codominant

Question 17

heterozygous phenotype is intermediate between the two homopygous phenotypes

Answer 17

incomplete dominance (semi-dominance)

Question 18

mutations in coding for the ATP7B protein that helps transfer excess copper into the blood stream or bile

Answer 18

Wilson’s Disease

Question 19

symptoms of Wilson’s disease

Answer 19

liver disease (cirrhosis), neurological problems, Kayser-Fleischer rings (corneal deposits of copper visible on eye exam)

Question 20

mitochondrial inheritance

Answer 20

matrilineal inheritance

Question 21

fraction of individuals showing mamifestations of a disease

Answer 21

penetrance

Question 22

the likelihood of manifesting the disease is dependent on age

Answer 22

age dependent penetrance

Question 23

the degree to which a trait is expressed

Answer 23

expressivity

Question 24

phenotypic expression is dependent on the individual’s sex

Answer 24

sex influence

Question 25

only one sex can express a phenotype

Answer 25

sex limitation

Question 26

inheritance of wilson’s disease

Answer 26

autosomal recessive

Question 27

inheritance of neurofibromatosis

Answer 27

autosomal dominant

Question 28

clinical presentation of neurofibromatosis

Answer 28

This is an example of a highly pleiotropic disorder
benign fleshy tumors (neurofibromas), cafe au lait spots, small benign tumors on the iris (Lisch nodules); less frequently: mental retardation, CNS tumors, diffuse plexiform neurofibromas, development of cancer of the nervous system or muscle

Question 29

mutation in neurofibromatosis

Answer 29

NF1 (codes for neurofibromin) mutation rate is 1 in 10,000 live births (really high!)

Question 30

inheritance of split hand deformity

Answer 30

autosomal dominant (can be in feet too)

Question 31

genetic disorders that can only be recognized at birth

Answer 31

congenital genetic disorders

Question 32

factors affecting pedigree patterns

Answer 32

reduced penitrance, variable expressivity, other genes and environmental factors, some may fail to survive at birth, new mutations, lack of information

Question 33

genetic heterogeneity

Answer 33

similar or same phenotype determined by genotypes at different loci (or same loci if different mutations which is also allelic heterogeneity)

Question 34

distinct phenotypes arising from the same allele

Answer 34

phenotypic heterogeneity (ex. Hirschsprung disease (chronic constipation) and multiple endocrine neoplasia 2A and 2B both are from different mutations in the RET gene)

Question 35

does CFTR have allylic heterogeneity?

Answer 35

YES, about 1400 different mutations have been found on the gene worldwide

Question 36

inheritance of cystic fibrosis

Answer 36

autosomal recessive

Question 37

Inheritance of sickle cell disease

Answer 37

autosomal recessive

Question 38

many different loci can result in the phenotype

Answer 38

locus heterogeneity (example: retinitis pigmentosa)

Question 39

alterations in the number of intact chromosomes

Answer 39

genome mutation

Question 40

mutations involving only part of a chromosome (partial duplication, triplication, deletion; inverstions, translocations

Answer 40

chromosome mutations

Question 41

changes in DNA sequence in nuclear or mitochondrial genomes

Answer 41

gene mutations

Question 42

example of amplified trinucleotide repeat in the coding region

Answer 42

huntington disease

Question 43

example of amplified trinucleotide repeat in the transcribes but untranslated region of a gene

Answer 43

fragile x syndrome

Question 44

unstable heritable element where the expression of a mutant phenotype is a function of the number of copies of the mutation

Answer 44

dynamic mutation

Question 45

multiple (>36) CAG repeats on the HD gene

Answer 45

huntington’s disease

Question 46

inheritance of huntington’s disease

Answer 46

Autosomal dominant

Question 47

when a genetic variant is found in more than 1% of chromosomes in the general popluation

Answer 47

genetic polymorphism

Question 48

p^2 + 2pq + q^2 = (p + q)^2

Answer 48

allelic frequencies under Hardy Weinberg equilibrium

Question 49

assumptions of Hardy-Weinberg Equilibrium

Answer 49

Random mating, large population, no appreciable rate of mutation, all genotypes are capable of mating, no immigration

Question 50

inheritance of achondroplasia

Answer 50

autosomal dominant

Question 51

common mutation of achondroplasia

Answer 51

on the FGFR gene which codes for a transmembrane recepto tyrosine kinase.
1138G>A (98%) and 1138G>C (1%) both result in Gly380Arg substitution

Question 52

what happens if two people with achondroplasia mate

Answer 52

they run the risk of passing two mutant genes (lethal combination if two copies of mutant gene)

Question 53

inheritance of hemophilia

Answer 53

X-linked recessive

Question 54

most common mutation in hemophilia A

Answer 54

an inversion mutation between sequences in intron 22 of F8 and a homologous sequence telomeric to F8

Question 55

most common mutation in hemophilia B

Answer 55

no most common mutation has been identified

Question 56

function of factors VII and IX

Answer 56

factor IX is a protease and Factor VIII is a co-factor. together they activate clotting factor X which, in turn, further activates factors VIII and IX

Question 57

define stochastic effects

Answer 57

chance mutation gives rise to a disease, ie radiation gives rise to a cancer